My girlfriend has one of these that she wears on her thumb. I love to take it off of her and put it on my pinky finger (it's the only finger that will fit her ring-size) and play with it when we're hanging out together. It really is a nifty ring.

One night, while making out, I realized that she had put one of the detachable straps of he bra through her ring and it was sitting there peeking out of her tank top. I asked her when she did that and takes off the strap, gives me the cutest smirk, and puts it on my right-hand ring finger. I don't give it another thought and we continue making out.

It wasn't until an hour later while snuggling, she says "Good guess, huh?" while playing with her ring on my hand. "What do you mean, 'good guess' ?" And then in a wave of realization, I figure out that it's not her ring on my hand, but one that she bought for me (she had taken her ring off earlier)! She had guessed my ring size perfectly and ordered me a ring! Yes, she put the ring on my right-hand ring finger and I should have realized it, but when you have a beautiful girl on top of you your brain gets a little fuzzy.

I get compliments on the ring all the time and it makes for a great conversation starter if people notice it, especially when I've got this story to share.

EDIT: for clarity. Also, she did not propose to me (although, she is a keeper!), she put the ring on my right ring finger. Traditionally, the guy proposes and places the ring on the left-hand ring finger.